Method for preparing 3, 3&#39;-5, 5&#39;-tetraalkyl-4, 4&#39;-diphenoquinones



NIETHOD FOR PREPARING 3,3'-5 ,5-TETRA- ALKYL-4,4'-DIPHENOQUINONESClarence S. Coe, Rolling Hills, Calif., assignor to Union Oil Company ofCalifornia, Los Angeles, Calif., a corporation of California i NoDrawing. Application February 4, 1952, Serial No. 269,891

6 Claims. (Cl. 260-396) This invention relates to improved methods forpreparing gasoline stabilizers of the 4,4'-dihydroxy diphenyl type,wherein all four positions ortho to the hydroxy groups are substitutedwith alkyl groups. In particular the invention concerns an improvedmethod for preparing 3,3'-5,5-tetra-alkyl-4,4'-diphenoquinones, whichmay be susequently reduced to the corresponding diphenols.

It is an object of this invention to provide inhibitors for gasolineswhich are highly effective in very small proportions.

A further object is to provide convenient and economical methods forpreparing such inhibitors.

Other objects will appear from the more detailed description whichfollows.

U. S. Patent No. 2,479,948 discloses a class of inhibitors which may bedesignated as 3,5,3',5'-tetra-alkyl-4,4'-dihydroxy diphenyls wherein notmore than two of the alkyl groups are tertiary alkyl groups. Thecompound 3,3'-5,5-tetra-tert-amyl-4,4'-dihydroxydiphenyl is disclosedtherein as being relatively ineffective as an inhibitor, being lessactive than the reference standard, cresylic acids. The other compoundsdisclosed, which contain primary and/or secondary alkyl groups, whilestated to be relatively active as inhibitors, are more or less solublein alkaline solutions. It has now been found that the specific compound3,3-5,5'-tetra-tert-butyl-4,4- dihydroxy diphenyl:

IDS Il)8 OH OH O(CHa)s ((CHr):

nited States Patent 0 tions in the presence of a copper catalyst toproduce a corresponding p-diphenoquinone, and then hydrogenating thediphenoquinone under mild hydrogenating conditions to produce thecorresponding dihydroxy diphenyl. These reactions may be summarized asfollows:

, STEPI R R R C 3 Q OH Hill O: =O+H8l Salt alkali on R1 R1 R1 STEP IIwherein R and R1 may be any inert substituents, but are preferablytertiary alkyl groups. 7

2,785,188 Patented Mar. 12, 1957 The prior art methods for preparingthese compounds have generally involved an oxidation of anon-halogenated phenol with strong acidic oxidizing agents such aschromic acid, followed by hydrogenation of the resulting diphenoquinone.The present process is carried out under mild alkaline oxidizingconditions at low temperatures, resulting in a minimum of undesired sidereactions and decomposition. The process is also easily controlled, andavoids the use of dangerous or corrosive reagents.

Examples of phenols which may be employed in Step I of my processinclude 2,6-di-tert-butyl-4-chlorophenol; 2,6 di isopropyl 4chlorophenol; 2,6 diethyl 4- chlorophenol; 2,6 dihexyl 4 chlorophenol; 2tertbutyl 6 ethyl 4 chlorophenol; 2 tert amyl 6- tert butyl 4chlorophenol; 2 tert butyl 6 cyclohexyl 4 chlorophenol; 2 methyl 4chlorophenol, or any of the bromo or iodo analogs of the abovecompounds.

The oxidizing conditions employed in Step I above generally involve airor other oxygen containing gas as the oxidizing agent. Finely dividedreduced copper powder is the preferred catalyst, although other metalpowders may be employed. The alkaline material acts as a halogenacceptor, and may be any alkaline acting material such as ammonia,calcium hydroxide, sodium hydroxide, primary, secondary or tertiaryamines, sodium carbonate etc. The reaction may be carried out at anydesired temperature and pressure. Normal atmospheric pressures and roomtemperatures are ordinarily preferred. A solvent such as ethanol may beemployed if desired. It is preferred that some water should be presentin the reaction mixture, since this appears to accelerate the reaction.If refluxing is employed it is preferred to employ either Water or somerelatively low boiling solvent in the reaction mixture in order tomaintain a reflux temperature below about C., thereby avoiding thermaldecomposition of the reactants or products. Air may be bubbled slowlythrough the mixture throughout the reaction period or a suitable solidor liquid oxidizing material may be present in the mixture.

After completion of the oxidation, the solid diphenoquinone, whichordinarily separates as bright red crystals, is filtered from themixture and washed with water to remove excess alkaline materials andsalts.

The diphenoquinone is then reduced with hydrogen under mildhydrogenation conditions, as for example with zinc and acetic acid, ortin and hydrochloric acid. Care must be exercised to insure that thehydrogenation conditions are not sufliciently drastic to cause thebenzene rings to also become partially or wholly hydrogenated. Only twoatoms of hydrogen are required to reduce the diphenoquinone to thecorresponding dihydroxy diphenyl. The above hydrogenating materials willordinarily add the desired hydrogen selectively at normal temperaturesand pressures. With higher temperatures and/or pressures,'or with othermore drastic hydrogenation catalysts, as for example Raney nickel, thereaction time must be closely controlled in order to avoid undesiredtypes of hydrogenation, or scission of the bicyclic structure.

After hydrogenation is completed, as may be evidenced by thedisappearance of color from the reaction mixture, the dihydroxy diphenylcompound may be recovered by filtration, washed with water, and ifdesired recrystallized from solvents such as alcohol, acetone, benzene,etc.

In order to illustrate the method of preparing these compounds, thefollowing examples are cited, which should be considered as illustrativeonly and not limitative:

Example IA 20 gms. of 2,6-di-tert-butyl-4-chrophenol was introduced intoa flask and treated at room temperature with a mixture of 70 ml.mono-n-butylamine, 20 ml. of water, and 0.2 gm. of copper powder. Airwas bubbled slowly through the mixture at atmospheric pressure for abouteight hours. During the reaction the mixture was observed to become redin color. Upon cooling, bright red needles of3,3'-5,5-tetra-tert-butyl-diphenoquinone, precipitated out, and wereseparated by filtration. Upon washing with water and recrystallizationfrom benzene, the crystals were found to have the followingcharacteristics:

Melting Point, 229 C.

Analysis:

Found H, 9.32%; C, 82.6% Calculated 9.86%; 82.3%

Mol.Wt.: I

Found 398 Calculated 408.6

The phosphomolybdic acid test for hindered phenols was negative.

Example I-B 15 gms. of the 3,3-5,5-tetra-tert-butyl diphenoquinone wasmixed in a fiask with about 3.0 gms. of zinc dust. Dilute acetic acidwas admitted periodically over a period of about 3 hours at roomtemperature. At the end of this period, the red color of the quinone wasobserved to completely disappear. The light colored crystals obtained oncooling were removed by filtration and washed with water. Uponrecrystallization fro-m benzene, pure3,3'-5,5-tetra-tert-butyl-4,4'-dihydroxy diphenyl was obtained in almostquantitative yield. The material had the following characteristics:

Melting Point, 184 C.

Analysis:

Found C, 81.1%; H, 10.2% Calculated C, 81.9%; H, 10.3% M01. Wt.:

Found 420 Calculated 411 The ultra violet spectra showed the typicalcharacteristics of phenolic OH groups when compared in ethanol andiso-octane solution.

Example [I 3 gms. of 2,6-di-tert-butyl-4-chlorophenol was dissolved in30 ml. of 95% ethanol and 0.1 gm. of copper powder was added. Air wasslowly bubbled through the mixture while 12 ml. of concentrated ammoniumhydroxide solution was gradually added. The reaction was continued atroom temperature for about 2 hours. At the end of the reaction periodexcess ammonia and alcohol was removed by distillation. The remainingsolid was water washed, then redissolved in benzene, filtered andrecrystallized. 3,3-5,5-tetra-tert-butyl diphenoquinone Was obtained inabout 80% yield, which gave upon hydrogenation the correspondingclihy-d-roxy diphenyl as in Example LS.

Example Ill Example 11 was repeated using a 10% sodium hydroxidesolution in place of the ammonium hydroxide. After 10 hours treatmentwith air at reflux temperature, a somewhat smaller yield of3,3-5,-5-tetra-tert-butyl diphenoquinone was recovered by thepurification procedure of Example II.

Example IV The procedure of Example I is repeated using as the startingmaterial 2,6-di-isopropyl-4-bromo phenol. A good yield of3,3-5,5'-tetra-isopropyl diphenoquinone is obtained, which gives3,3-5,5'-tetra-isopropyl-4,4-dihydroxy diphenyl upon mild hydrogenationwith tin and hydrochloric acid. a

The procedures outlined in the above examples may be employed forpreparing substantially any substituted 4,4- dihydroxy diphenyl byemploying as the starting material the appropriate substituted4-halophenol in place of the halophenols employed in the examples. Theslight modifications of procedure which may be necessary to accommodatethe slight difierences in solubility and reactivity of the variousstarting materials will be obvious to those skilled in the art. Theabove procedures are particularly valuable for preparing stericallyhindered dihydroxy diphenyls, wherein the reactivity of the phenolgroups is hindered by the presence of a tertiary alkyl group in each ofthe positions ortho to the hydroxy groups.

The compound prepared in Example I-B, namely 3,3-5,5-tetra-tert-butyl-4,4-dihydroxy diphenyl is found to be particularlyvaluable as an inhibitor for petroleum products. It is active in smallproportions, ranging from about 0.0001% to 0.2%, and is very insolublein aqueous alkaline solutions, such as the alkaline solutions employedin sweetening gasoline stocks. While this material is particularlysuitable for use in cracked gasolines, it is also satisfactory for useas a stabilizer in other oxidizable organic compounds such as aviationgasoline, turbine oils, lubricating oils, unsaturated hydrocarbonpolymers, resins, turpentine, corn oil, cottonseed oil, fish oils,animal oils, fats, oils, soaps, terpenes, essential oils, celluloseesters and ethers etc. The proportion of inhibitor to be used in thesematerials is within the same range as mentioned above in connection withpetroleum products. With cracked gasolines, about 10 pounds of theinhibitor per 1,000 barrels of gasoline may suitably be used, whichcorresponds to about 0.0035% by weight.

Cracked gasolines containing from 0.001% to 0.1% of3,3-5,5-tetra-tert-butyl-4,4'-dihydroxy diphenyl are found to exhibitsubstantially increased induction periods when tested according to thestandard oxygen absorption test. In this test oxygen is bubbled throughthe sample of gasoline at 150 C., and the time required for a givenamount of oxygen absorption is measured. This test, while being astandard method, does not necessarily correlate accurately in allgasoline stocks with the overall stability in actual use of theparticular gasoline. For gasolines derived from western crudes, a morereliable index of stability is usually obtainable by a determination oftheir peroxide content. High peroxide numbers indicate low stability andlow peroxide numbers indicate high stability. These peroxide numbers aredetermined by titrating a sample of the gasoline with a reducingsolution consisting essentially of 0.01 N titanous chloride. This methodis more particularly described in U. 0. P. Laboratory Test Methods forPetroleum and its Products, Universal Oil Company (1940).

Example V Peroxide No.

Sample after 24 after 72 alter 17 hours hours days exposure exposureexposure to air to air to air 75 This data hows that3,3-5,5'-tetra-tert-butyl-4,4' dihydroxy diphenyl is efiective inextremely small amounts in preventing the formation of peroxides incracked gasolines, and that it retains its activity for a longer periodof time than its monocyclic analog, 2,6-di-tert-butyl p-cresol. Inasmuchas these peroxides are considered to be precursors or essential factorsin the formation of gums in gasolines, it is clear that the abovecompound is a highly effective stabilizer.

The foregoing disclosure of this invention is not to be considered aslimiting since many variations may be made by those skilled in the artwithout departing from the scope or spirit of the following claims.

Iclalim:

l. A method for preparing a 3,3-5,5-tetra-alkyl-4,4'- diphenoquinonewhich comprises oxidizing a 2,6 dialkyl 4-halophenol with a mildoxidizing agent in the presence of an alkaline-acting material and ametallic copper catalyst.

2. A method as defined in claim 1 wherein said oxidizing agent is anoxygen-containing gas.

3. A method for preparing a 3,3'-5,5'- tetra-tert-alkyl- ReferencesCited in the file of this patent UNITED STATES PATENTS Tishler et al.Feb. 23, 1943 Luten et a1 Aug. 23, 1949 OTHER REFERENCES ChemicalAbstracts, vol. 32, Co]. 5802-5803 (1938).

Abstracting an article of C. V. Bordeianu in Ann. Sci.

University, Jassy, Pt. I, 23.

1. A METHOD FOR PREPARING A 3,3''-5,5''-TETRA-ALKYL-4,4''DIPHENOQUINONEWHICH COMPRISES OXIDIZING A 2,6 DIALKYL 4-HALOPHENOL WITH A MILDOXIDIZING AGENT IN THE PRESENCE OF AN ALKALINE-ACTING MATERIAL AND AMETALLIC COPPER CATALYST.